Jerusalem (CNN) -- Israeli forces dropped leaflets in northern Gaza on Sunday to warn residents to move away from Hamas sites immediately to avoid airstrikes.
The death toll from the Israeli airstrikes on Gaza has topped 160 in several days, the Gaza health ministry said. More than 1,100 people have been injured.
About 70% of Gaza fatalities are civilians, of which 30% are children, said Chris Gunness, spokesman for United Nations Relief and Works Agency for Palestine Refugees.
Israel says it's defending its citizens from the hundreds of rockets fired into its territories by militants from Gaza.
In an attempt to avoid more deaths, Israel issued advance warning on airstrikes.
"The Israeli Defense Forces intends to attack terrorists and terror infrastructures ..." the leaflets said, mentioning a list of areas that will be targeted.
"Israel is currently attacking, and will continue to attack, every area from which rockets are being launched at its territory."
But some residents said they will not leave.
"They will not vacate ... where do we go?" asked Ramez Al-Madhoun, who lives in a building with 20 people in Beit Lahya. He said his building has seven adults, the rest were children. In the background, rockets rang out from his northern Gaza neighborhood.
The Israel military said it also drops empty shells on roofs, an operation it calls "roof knocking," to alert civilians that airstrikes are imminent.
The goal of the airstrikes, the military said, is to get Hamas militants to stop firing rockets into Israel.
More than 800 rockets have been fired from Gaza to Israel in the past week of escalated tensions, according to the Israeli military. Of those, nearly 150 have been intercepted by Israel's Iron Dome.
Israel said its forces have struck 1,320 "terror targets" across the Gaza Strip, including 735 concealed rocket launchers.
Hostilities between the two sides escalated this month after the killing of three Israeli teenagers and a Palestinian teen. Neither Hamas nor Israel appear to be backing down.
Concerns about a ground invasion by Israeli forces are growing, prompting the U.N. Security Council to call for a cease-fire between Israeli forces and Palestinian militants.
A day after the cease-fire appeal, Israeli forces briefly entered Gaza early Sunday and raided a missile launching site.
This is the first time Israeli forces have acknowledged they've entered Gaza in the current conflict.
During the incursion, which lasted about half an hour, both sides exchanged gunfire at the launch site, an Israeli military source said.
Four Israeli troops suffered light injuries, but all the soldiers returned home safely, the source said.
The source declined to comment on whether the mission achieved its objective.
Days of tensions
Hamas has rained hundreds of rockets on Israel in recent days, prompting the latter to respond with airstrikes.
Though some Israelis have been wounded, none have been killed by the rockets fired by Hamas and other militant groups in Gaza. Israel's Iron Dome defense system has intercepted dozens of rockets, helping keep fatalities at bay.
Dozens of Palestinian children killed
Israel asserts its right to defend itself, and so far the Hamas rockets have caused no deaths. Hamas says it's firing rockets in self-defense.
"What about the right for the Palestinians to protect themselves to protect their people?" Hamas spokesman Osama Hamdan. "The international solution is asking Israel to leave, but they're not doing that."
More than 3,000 Palestinians are displaced and hundreds of thousands have been affected by damage to water infrastructure, said the United Nations Relief and Works Agency for Palestine Refugees.
At least 28 Palestinian children have died in the recent fighting, and others are beginning to show signs of mental distress, said Catherine Weibel, communications chief for the United Nations Children's Fund.
CNN's Faith Karimi wrote and reported from Atlanta, and CNN's Michael Schwartz and Salma Abdelaziz reported from Jerusalem. CNN's Khalil Abdallah contributed to this report.